1. Field of the Invention
The present invention generally relates to the repair of electronic circuit modules and, more particularly, to the repair and recovery of circuit modules with defective solder ball connectors. The invention has particular application in the repair of integrated circuit (IC) chips requiring repair of solder ball connectors in an array of solder ball connectors on high density chips. IC chips are but one example of electronic circuit module, and other electronic circuit modules or interconnection devices employing arrays of solder balls may be repaired using the invention.
2. Description of the Prior Art
Chips can have many defects relating to solder balls. Chips with plated or evaporated solder balls may have solder ball mechanical damage, solder pads covered with foreign material, or random low volume pads. High density complimentary metal oxide semiconductor (CMOS) chips may contain as many as 4000 solder ball pads and are very expensive to replace if rejected because of solder ball defects.
It becomes necessary to modify or customize the electrical net list to fit a particular performance criteria. These modifications are called Engineering Changes (ECs). The Engineering Change process is complex, involving laser deletes and wire adds, and results in a considerable backlog of modules in the build, assembly and test (BAT) process during high volume production. Most of the congestion is caused by the need for wiring changes in configuring the electrical functionality of a large system. Temporary wiring changes need to be removed and restored to original circuitry causing even further congestion or delays in productivity in a high volume line.
A solder paste system may be used to repair chips with damaged solder balls. This system is limited to large pitch solder balls and cannot be used effectively on high density CMOS chips. The solder paste system has problems dispensing consistent solder volumes, as well as introducing contamination from paste materials.